1. Department of Molecular Cell Biology, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.
2. Posung High School, Seoul 138-050, Korea.
3. Department of Anatomy, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.
4. Center for Molecular Medicine, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.